Chromophobe adenomas account for approximately 85% of pituitary tumors. While these patients may present with pituitary apoplexy or interference with visual pathways many are detected during the evaluation of headaches, chronic endocrine hypofunction, and as an incidental finding. Therapy for these latter groups is not uniform and includes various radiation modalities and pituitary surgery. What little data is available (all retrospective) suggests that patients with pituitary tumors but no visual impairment may not demonstrate deterioration after 10-15 years follow-up. The question is raised as to whether the risks of radiation therapy and surgery are justified if the natural history of these tumors in those patients without visual field defects is, in fact, relatively benign. The purpose of this project is to observe in a randomized fashion the natural history of chromophobe adenomas which have not initally produced a visual field defect. Patients will either be treated with conventional pituitary irradiation or observed untreated. In addition, specific clinical and laboratory abnormalities which will guide the physician in his treatment of these patients may be identified. This project is estimated to last 10 years and involve at least 50 patients.